XPost: uk.d-i-y
From: diverse@tcp.co.uk
On 03/02/2025 20:05, Liz Tuddenham wrote:
> N_Cook wrote:
>
>> On 03/02/2025 17:45, Liz Tuddenham wrote:
>>> N_Cook wrote:
>>>
>>>> Only made a preliminary check o this 1KW pump and float switch in a
>>>> sump, prior to dismantling ad exploring further.
>>>> Sump full of water but no pump action. Moving the float about made no
>>>> differece. Tapping the pump casing made the pump work until the float
>>>> switch dropped to the cut off point.
>>>> Refilling the sump and again no pump action until tapping the casing and
>>>> again stopping properly. I cannot see what in the way of sticky motor
>>>> brush or loose/corroded contact inside the motor housing could produce
>>>> this symptom.
>>>
>>> You haven't said what sort of motor it is, but if it is a commutator
>>> motor with brushgear, the fault could be worn-down brushes to the point
>>> where one of them is almost-but-not-quite touching the commutator.
>>> Tapping the motor gives some sort of contact and then the vibration of
>>> the motor allows it to touch the commutator often enough to keep it
>>> running. This will give a fireworks display around the commutator and
>>> will do considerable damage if it continues.
>>>
>>> If it is not a brush motor, a similar thing can happen if the terminals
>>> have become loose. The sudden shock torque as the motor starts is
>>> enough to make contact and vibration will keep it running; then the
>>> contact is lost again after the motor has stopped.
>>>
>>> The first things you need to check are what type of motor it is and
>>> whether the supply is reaching the terminals in the connection box on
>>> the motor casing.
>>>
>>
>> The pump is a JTFS Mini Micro domestic sewage pumping station,
>> probably JTFS190NN
>> No type technical details found but no obvious external starter cap
>> outside the motor casing or casig bulge.
>
> They are rated for AC only, so most unlikely to be a brush motor (which
> might also be too noisy in this application). If there is no visible
> capacitor, it could be an induction-start motor or the capacitor is
> hidden in the control box.
>
> When it starts, is there s "snick!" noise as it reaches running speed?
> That would be a centrufugal starting switch throwing out - and when the
> motor is switched off, as it slows down, you might hear the switch go
> "Snick! " again as it resets.
>
>> The other consideration is it was installed 10 years ago, tested working
>> then, but never heard to be working since.
>
> That absolutely rules out any sort of wear-related pronlem. It would be
> the sort of situation where the starting switch contacts become corroded
> through lack of use. A slight tap causes them to make contact and the
> starting current (which is usually quite large) blows some of the
> corrosion away. After a few starts like this, you may find it appears
> to work properly.
>
>> It should have worked in a flood situation last year but it did not
>> (automatically of its own accord that is) , no maintainece or testing or
>> inspection in those 10 years by the owner or anyone else.
>
> If mild corrosion in the starting switch is the cause of the problem,
> testing it, say, once every couple of months should keep it healthy. If
> water has penetrated the casing, you will eventually have a much bigger
> problem - you need to check for that with a 500v tester, just in case.
>
It is protected by a RCCD/ELCB that has never tripped out over 10 years.
But when I said tapping the motor, I used an insulated stick JIC.
Next visit I'll take a plastic stethoscope to have a better listen for a
cetrifugal switch, but i can see a corrossion or mechanical problem
there giving the repeatable no-go/go on tap symptom.
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